Keyboard switch assembly with improved movable contact having cantilever supported central member with radially extending contact fingers

ABSTRACT

A mechanically operated keyboard with key stations having a multiplicity of electrical switch contacts for providing an encoded electrical data output signal corresponding to and uniquely identifying individual key stations includes an array of movable contacts each corresponding to an individual key station and which are formed in a sheet of conducting material mounted above a corresponding array of fixed contacts to form multiple contact electrical switches for each key station of the keyboard. Each movable contact has a central member suspended to the sheet of conducting material in cantilevered fashion and includes a plurality of peripherally spaced contact fingers joined to the central member such that the contact fingers adjacent the junction of the central member to the conducting sheet will contact associated fixed contacts of a key station only after the remaining contact fingers have come into contact with their associated fixed contacts. An electrical circuit coupled to the contact fingers provides a strobe output signal only when all of the electrical switch contacts associated with a given key station have been actuated as indicated by the closure between the contact finger adjacent the junction of the central member to the conducting sheet and its associated fixed contact.

United States Patent 1 1 Hatley et al.

[ 11 3,777,082 i 1 Dec.4,1973

[75] Inventors: Derek J. Hatley, Wyoming; Harold R. Wilson, Holland,both of Mich.

[73] Assignee: Donnelly Mirrors, Inc., Holland,

Mich.

[22] Filed: Sept. 8, 1972 [21] Appl. No.: 287,508

[52] US. Cl 200/5 A, 200/159 B, 200/166 8H [51] Int. Cl. Hlh 13/14 [58]Field of Search 200/ R, 5 A, 159 B,

ZOO/166 BH, 1 R, 159 A, 166.]

[56] References Cited UNlTED STATES PATENTS 3,600,528 8/1971 LeposavicZOO/159 B X 3,627.935 12/1971 Spievak 200/5 A X 3,697,711 /1972 Tetrick200/5 A X Primary Examiner-J. R. Scott Atr0rneyPeter P. Price et a1.

[5 7] ABSTRACT A mechanically operated keyboard with key stations havinga multiplicity of electrical switch contacts for providing an encodedelectrical data output signal corresponding to and uniquely identifyingindividual key stations includes an array of movable contacts eachcorresponding to an individual key station and which are formed in asheet of conducting material mounted above a corresponding array offixed contacts to form multiple contact electrical switches for each keystation of the keyboard. Each movable contact has a central membersuspended to the sheet of conducting material in cantilevered fashionand includes a plurality of peripherally spaced contact fingers joinedto the central member such that the contact fingers adjacent thejunction of the central member to the conducting sheet will contactassociated fixed contacts of a key station only after the remainingcontact fingers have come into contact with their associated fixedcontacts. An electrical circuit coupled to the contact fingers providesa strobe output signal only when all of the electrical switch contactsassociated with a given key station have been actuated as indicated bythe closure between the contact finger adjacent the junction of thecentral member to the conducting sheet and its associated fixed contact.

16 Claims, 8 Drawing Figures PATENTEDUEE 4191s 3.777.052

SHEET 2 OF 3 a ll KEYBOARD SWITCH ASSEMBLY WITH IMPROVED MOVABLE CONTACTHAVING CANTILEVER SUPPORTED CENTRAL MEMBER WITH RADIALLY EXTENDINGCONTACT FINGERS BACKGROUND OF THE INVENTION The present inventionrelates to an electricalmechanical keyboard for producing data outputsignals, and particularly to the switch construction for providing dataoutput and strobe signals when all of the switch contacts of anindividual key station are closed.

Conventional keyboards are either electricalmechanical or electrical indesign. With the advent of computer applications whereby the outputsignals from a keyboard are coupled directly to various computerterminal equipment, it has become necessary to provide multiple bit dataoutput signals from the keyboards which accurately and rapidlycorrespond to an actuated key station. Conventional electricalmechanicalkeyboards are relatively unsuccessful in such applications partiallybecause of contact bounce occurring with the electrical switchesemployed. Also, errors in the data output signals frequently are causedby timing differences between the closing of individual switchesassociated with each key station. Thus, computer inputs to whichconventional keyboards are coupled, and which are relatively fastreading, interpret contact bounce and/or timing lags as an erroneouscode or data signal. The keyboard of the present invention, however,employs a unique switch design which has a single movable electricalcontact with a plurality of contact fingers which, together with amultiplicity of fixed contacts, form electrical switches. A digitalcontrol circuit is coupled to the keyboard and insures that no dataoutput signals are read by the computer or interface equipment until allof the switch contacts are properly closed. This design overcomes thedifficulties faced by conventional mechanical keyboards.

Electrical keyboards employing Hall-effect devices, reed switches,capacitive devices, or magnetic devices are frequently more reliablethan many electricalmechanical keyboards but are considerably morecostly, The keyboard of the present invention, however, providesreliability equivalent to such electrical keyboards but at a greatlyreduced cost.

An electrical-mechanical keyboard using a single movable contact with aplurality of contact fingers has employed a last-to-close contact fingerassociated with the switch contacts to provide a signal when all of theswitch contacts have been made. The design however employs contactfingers which are bent at different angles relative to the remainingfingers and must be accurately formed to insure its operation. Thedesign of the present switch eliminates the difficulties encounteredwith the manufacture and operation of such a switch.

SUMMARY OF THE INVENTION fixed contacts is coupled to a source ofoperating power and to a keyboard output terminal to provide electricaldata output signals therefrom when a key station is actuated. A strobepulse generation circuit is coupled to at least the receivable contactadjacent the cantilever mounting point to generate a strobe signal onlywhen this last-to-close contact is closed and thereby all of theremaining movable contact fingers have contacted associated fixedcontacts. This assures that an accurate data output signal is present atthe keyboard data output terminals when a strobe pulse is generated.

It is an object, therefore, of the present invention to provide a novelswitch construction for use with a mechanically operated keyboard havinga plurality of key stations each with a movable contact having aplurality of contact fingers associated with fixed contacts such that atleast one switch contact will close only when all of the remainingswitch contacts of a key station have been closed.

It is another object of the present invention to provide a movablecontact mounted to a contact finger sheet in a cantilevered fashion suchthat as the movable contact is actuated, contact fingers attachedthereto and adjacent the cantilevered mounting point are lastto-make.

It is still a further object of the present invention to provide animproved electrical-mechanical keyboard.

These and other objects of the present invention will become apparentupon reading the specification together with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a keyboardembodying the present invention;

FIG. 2 is a side elevation view in cross section of an individual keystationemployed in a keyboard embodying the present invention;

FIG. 3 is a wiring diagram showing the interconnection of the fixed keystation contacts to the keyboard output terminals for the letters D" andF, and also showing the electrical and mechanical relationship of themovable contacts associated with the fixed contacts for the key stationsD and F.

FIG. 4 is an electrical circuit diagram partially in schematic and blockdiagram form showing one embodiment of a keyboard embodying the presentinvention;

FIG. 5 is an enlarged partial plan view of a movable contact sheetshowing the detailed structure of one embodiment of the movable contactof one of the key stations of the keyboard;

FIG. 6 is a section view of the structure shown in FIG. 5 taken alongthe section lines VI-VI together with the associated fixed contacts;

FIG. 7 is an enlarged partial plan view of the movable contact sheetshowing the detailed structure of one alternative embodiment of themovable contact of one of the key stations; and

FIG. 8 is an enlarged partial plan view of the movable contact sheetshowing the detailed structure of another alternative embodiment of themovable contact of one of the key stations.

DETAILED DESCRIPTION OF THE FIGURES Referring now in detail to FIGS. l3,there is shown a mechanically operated electrical keyboard including aplurality of key stations 10 for each symbol shown in FIG. 1. Thekeyboard 100 has a plurality of output terminals A-P for couplingelectrical output signals from the keyboard to various circuitsassociated with the keyboard. The keyboard comprises a face plate 28with an array of apertures 29 in which the key stations 10 are mounted.Each key station includes a key cap 12 (FIG. 2) which corresponds to anindividual letter, number, or other symbol which is desired to beentered into a computer or other digital interface equipment in the formof an electrical data signal corresponding to and uniquely identifyingthe symbol. The cap 12 is coupled over a plunger assembly 20 that ismoved downwardly when the key station is actuated by the operator. Theplunger assembly 20 comprises an end portion 21 over which the cap 12 ismounted, a cylindrical sleeve 22 joined to the member 21; and a plunger23 slidably mounted within the sleeve 22 which in turn is slidablymounted within a housing 25. A spring 23 couples the plunger 23 to themember 21. A return spring 27 is coupled to the outer periphery of thehousing 25 and extends upwardly to contact the end member 21 to returnthe key to its original position when released by the operator. Thehousing 25, which accommodates the sleeve 22, is fitted within anaperture 29 in face plate 28 of the keyboard to hold the individual keystation 10 into position on the keyboard.

The plunger 23 contacts a flexible sheet 30 of insulating material suchas rubber which spans the entire array of key stations forming thekeyboard and which has adjacent its surface opposite the plunger 23, asheet 35 of flexible conducting material 40 such as beryllium copperwhich is selectively etched away at the area immediately under each ofthe plungers 23 of each key station to form an array of movableelectrical contacts 50. Each key station 10 includes a movableelectrical contact shown in FIG. which, as described in detail below,comprises a plurality of individual contact fingers formed around theperiphery of a central portion of conducting material that iselectrically and mechanically formed in the sheet 35 of conductingmaterial 40 by means of a cantilevered attachment to the sheet 35. Thespecific movable contact structure of FIGS. 5-7 and their constructionis discussed below.

Under the movable contact 50 of the key station (FIG. 2) is an array offixed contacts 70 which are mounted in alignment with the contactfingers of the movable contact on an insulated base material 72 whichserves to rigidly hold the fixed contacts 70 in place. The flexibleinsulating material 30 and the conducting sheet 35 are supported abovethe base 72 by means of support members 74 which are spaced to allow thekey plunger 23 to depress the movable contact sufficiently when the keystation is actuated so as to cause physical and electrical contactbetween the movable contact 50 and the array of fixed contacts 70 on thebase. Each of the individual contacts 70 forming the array of fixedcontacts are electrically coupled to output terminals AP (FIGS. 1 and 3)of the keyboard 100 by means of conductors 75 (FIG. 3) which, like thefixed contacts 70, can be deposited on the base member 72 as iswell-known in the art. The fixed contacts 70 of each of the key stations10 forming the keyboard can likewise be formed on a printed circuitboard having a layer of conducting material that is selectively etchedaway to form the individual fixed contacts and their leads to theterminals A-P at the edge of the board.

The movable contact fingers of each key station are formed in the sheet35 of conducting material 40 (FIG. 2) to form a finger sheet 45 which iselectrically grounded as shown in FIGS. 3 and 4. The fixed contacts forthe individual key stations and their leads coupling the fixed contactsto the keyboard output terminals are likewise shown schematically inFIGS. 3 and 4. A voltage source +V is coupled to each fixed contact ofevery key station through a plurality of voltage dropping resistors76-91 to provide electrical operating power for the keyboard. As anindividual key station is actuated, the contact fingers of the movablecontact 50 on finger sheet 45 (FIGS. 3 and 4) contact the array of fixedcontacts coupled to a predetermined number of resistors 76-91 such thata predetermined number of the output terminals A-P are grounded. Thevoltage at these output terminals thereby drops to zero providing alogic 0 output at the terminals where a movable contact finger haselectrically contacted an associated fixed contact. The remainingoutputs remain at the voltage of the +V source or a logic 1 level. Eachkey station will have an array of fixed contacts of a sufficient numberto provide a data signal to uniquely identify that particular stationand, if desired, check line signals. The output terminals A-K providethe data signals whereas terminals L-P provide check signals employed asexplained below to insure proper closure of the contacts of a keystation before a strobe pulse is generated.

The key stations for the letters D and F are shown in FIGS. 3 and 4.Letter D has fixed contacts 70D coupled to resistors 76, 79, 80, 87, 88and 91 via conductors 75. Thus, when the key station corresponding tothe letter D is actuated, output terminals A, D, E, L, M and P will havea logic 0 output since the fixed contact associated with these outputterminals will be grounded on the opposite side of the voltage droppingresistors. The remaining output terminals will remain at the logic 1state. Similarly, when the letter F key station is actuated by theoperator, output terminals A, C, F, G, I, K, L, M and P will have alogic 0 signal due to the closure of movable contact 50F with fixedcontacts 70F and the coupling of interconnecting conductors 75 of thekey station.

The output terminals A-K which develop the data output signal uniquelyidentifying each key station as it is actuated are coupled tocorresponding input terminals A-K of a code conversion logic circuit 95.Circuit 95 (FIG. 4) is a conventional circuit which detects the logic 1and 0 states on lines A-K and converts these signals to standard 7-bitdata signals employed with conventional computer equipment and whichap-' pear on data output lines 1-8 coupled to circuit 95. The codeconversion logic circuit 95 includes a shift key 97 associated with thekeyboard and electrically coupled thereto which serves to actuatecircuit 95 to respond to provide a different data output signal for akey station when the shift key is actuated by the operator.

A strobe pulse generation circuit 1 10 has input terminals coupled tothe check lines L-P to receive signals therefrom which actuates thecircuit to develop a strobe output pulse at terminal 112 when the switchcontacts of a key station are actuated. In some embodiments, the strobepulse generator 110 may include associated circuits which providevarious features in conjunction with the keyboard of the presentinvention such as two-key roll-over Such associated and includedcircuits are described in detail in a copending patent applicationentitled KEYBOARD AND DIGITAL CIR- CUIT THEREFOR by Derek I-Iatley,filed concurrently herewith, assigned to the present assignee; andincorporated by reference herein. In its less complex embodiment, thecircuit 110 receives a signal from one of the check lines coupled to thelast-to-close switch contact for each key station and includesconventional pulse generating and shaping circuits which respond theretoto provide the desired strobe output signal when all of the switchcontacts of a key station have been actuated. One switch contact signedto provide such a signal to the strobe pulse circuit is shown in detailin FIGS. 5 and 6.

Referring now in detail to FIG. 5, there is shown a movable contactstructure 50 which comprises a central member 52 which is suspended in acantilevered fashion to the flexible conducting material 40 and formedas an integral part thereof by means of a coupling means 54. Means 54comprises a generally Y- shaped member having an arcuate segment 55joining in a cantilevered fashion by means of member 53, the centralmember 52 to the edge 56 of a central aperture 57 formed in theconducting material 40. Aperture 57 is sufficiently large to accommodatethe contact finger assembly 50 therein which is shaded in the figure forclarity. Member 55 has arms 51 at opposite ends which join the centralmember 52 to the arcuate segment 55 thereby electrically andmechanically coupling the member 52 to the sheet 40.

Around the periphery of the central member 52 is formed a plurality ofcontact finger pairs 58 and 59. 12 pairs of contact fingers are shown inthe figure. It is understood that this number can be varied fordifferent keyboard needs. The central member 52, the contact fingers 58,59 and the assembly 54 are formed as an integral part of the contactfinger sheet 40 by, for example, selectively etching away the material40 to form the structure shown in FIG. 5. An array of such movablecontacts is formed in the finger sheet 45 such that each key station ofthe keyboard has a movable contact.

In FIG. 4, the contact fingers 58, 59 and associated fixed contacts 70for the letters D and F are identified as 58D, 70D and 58F, 70Frespectively.

At least three of the contact fingers are formed on the central member52 adjacent the arm 53 joining the arcuate segment 55 to the edge 56 ofthe sheet 40 and are indicated at 59 in the figure. As explained below,these contacts (59) will contact associated fixed contacts 70 after theremaining contact fingers 58 have contacted their associated fixedcontacts. FIG. 6 illustrates the operation of the movable contact toinsure this result.

For the sake of clarity, only two oppositely positioned fixed contacts70 are shown in FIG. 6. These contacts are aligned with the movablecontact 59 closest to arm 53 and the movable contact directly oppositethe central member 52 and identified as 58' in FIG. 5. Before a keystation is actuated, the movable contact 50 is co-planar with the sheet40 such that the plane of the central member 52 is substantially in theplane of the remaining portion of the sheet 40. Once the key is actuatedand the plunger 23 '(FIG. 2) contacts the central member 52 through theinsulating sheet 30, and before the key is fully depressed, the movablecontact is in a position illustrated at A in solid lines in FIG. 6. Inthis position, the plane of the central member 52 is approximately thesame as the plane of the arcuate segment 55. Arm 53 is tilted at anangle with respect to the sheet 40 and the plane of the surface of thefixed contacts such that the contact finger 58 is approximately first tocontact its associated fixed contact 70. Up until this point, themovement of the plunger 23 has only caused the arm member 53 to bendthereby allowing the central member and contact fingers thereon to tiltdownwardly as shown in position A.

As the plunger 23 continues its downward travel as indicated by thedirection of the arrow shown in FIG. 6, the central member 52 andcontact fingers 58 and 59 thereon pivot in a twisting fashion about theend connecting members 51 of the assembly 54 causing them to bepositioned as shown in the phantom lines at position B in FIG. 6. Thepivoting of the central member 52 about the end members 51 insures thatthe contact finger 59 closest the arm 53 will contact the associatedfixed contact last. The closure of this contact therefore can beemployed to generate a strobe pulse indicating that all of the remainingcontacts have been made. It is seen that the remaining contacts 59 whichare also adjacent the arm 53 likewise tend to close last and the threecontacts 59 closest the arm 53 can be used in combination to provide astrobe pulse only after all three have closed. In such an arrangement,the strobe pulse generator 110 (FIG. 4) includes a three input AND gatewhich provides an output pulse only after the three contacts which arecoupled to the inputs of the AND gate have closed. In most circuitshowever, only the contact finger 59 closest the arm 53 is used.

FIG. 7 shows one alternative embodiment of the movable contact 50 inwhich the central member 52 is joined to the edge 56 of the conductingsheet 40 by means of a pair of arms 53' and 54' which replace theassembly 54 shown in FIG. 5. The operation of the movable contact fingershown in FIG. 7 is substantially the same as that shown in FIG. 6. Asthe plunger 23 (FIG. 2) is actuated and moves downwardly, the centralmember 52 will first bend about the narrowed portions 55 of the arms 53and 54 such that the movable contact assumes the position A shown inFIG. 6. After the'contact finger 58" which is opposite members 53' and54 contacts an associated fixed contact, the central member 52 willpivot about the narrowed portions 57' of arms 53' and 54 to the positionshown in FIG. 6 at B thereby causing the contact finger 59 (FIG. 7) tocontact its associated fixed contact last. This contact finger pair cantherefore be used to generate a strobe pulse in the same manner asdescribed above and insures that a strobe pulse is generated only afterthe remaining contact fingers 58" and 58 have contacted their associatedfixed contacts.

Another embodiment of the movable contact is shown in FIG. 8. In thisembodiment, the central member 52 is supported by the combination of apair of arms 61 and 63 and arcuate arm 65. Each arm 61, 63 is coupled atone end to the central member 52 and at an opposite end to arcuate arm65. Arm 65 extends approximately l around the central member 52 and isformed by etching out an arcuate slot 66 in the conducting material 40.The contact shown in FIG. 8 also includes twelve contact finger pairs 62around the periphery thereof. The movable contact so formed operates ingenerally the same manner as illustrated in FIG. 6 by first flexing atthe junction of arms 61 and 63 with arcuate arm 66 until some of thecontact finger pairs have contacted their associated fixed contacts andthen bending at the junction of the ends of arcuate arm 65 with theremaining portion of a contact finger sheet 40 until the last-to-makecontact positioned between arms 61 and 63 contacts its associated fixedcontact.

It is seen therefore that the embodiments shown in FIGS. 5, 7 and 8provide movable contact fingers which are mounted in a cantileveredfashion to the contact sheet 40 and which provide last-to-closecontacts. These contacts are used with the circuitry shown in FIG. 4 togenerate a strobe output signal which is coupled to the interfaceequipment causing the interface equipment coupled to the keyboard toread the data output signal from the keyboard only when all of theswitch contacts are properly actuated as indicated by the last-to-closecontact being made. This insures that an accurate data signal is read bythe interface equipment. As noted in the copending applicationidentified above, various digital circuits for providing two-keyroll-over and other features, can be employed with the movable contactsshown in FIGS. and 7 to provide a more flexible keyboard with suchadditional features although the keyboard described herein is capable ofproviding accurate data output signals at a relatively low cost byvirtue of the switch construction.

It will be apparent to those skilled in the art that the specific designof the movable contacts can be varied to provide the same desired effectsuch that when the cantilevered movable contact is actuated by theplunger, one of the contacts thereon will be last-tomake and therebyprovide a strobe pulse generating signal. Also the contact finger pairsmay include a single member instead of the two-pronged membersillustrated. These and other modifications will however fall within thescope of the present invention as defined by the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows.

1. In a keyboard including a plurality of key stations for providingelectrical data signals uniquely identifying each key station as it isactuated, an electrical switch for each key station comprising:

an insulated base member;

an array of fixed electrical contacts positioned in fixed relationshipon said base member;

insulative spacing means on said base member adjacent said array offixed electrical contacts;

a sheet of flexible conducting material supported on said spacing meansin spaced relationship to said array of fixed electrical contacts andincluding an opening therein;

a movable electrical contact positioned within said opening of saidsheet, said movable contact including a central member with a pluralityof contact fingers positioned in alignment with associated fixedelectrical contacts and means coupling said central member to an edge ofsaid sheet adjacent said opening in a manner such that when the keystation is actuated, said central member moves in a controlled manner toassure a predetermined contact finger will contact an associated fixedcontact last in the sequence of engagement of said contact fingers tosaid fixed contacts.

2. The apparatus as defined in claim 1 wherein said coupling meanscomprises an arcuate segment of flexible conducting material havingopposite ends coupled to said central member such that said segmentcircumscribes a portion of said central member, and

means for joining an edge of said segment remote from said centralmember to an edge of said sheet within said opening in a cantileveredfashion such that when the key station is actuated, said central memberwill initially bend about said joining means and subsequently pivotwithin said segment at the junction of said opposite ends of saidsegment to said central member such that the contact finger immediatelyadjacent said joining means is last-tomake.

3. The apparatus as defined in claim 2 wherein said joining meanscomprises an arm coupled between said segment and said edge of saidsheet; and wherein said central member and contact fingers thereon, saidsegment, and said arm are integrally formed in said sheet and aresubstantially coplanar therewith when the key station is not actuated.

4. The apparatus as defined in claim 1 wherein said means for couplingsaid central member to said sheet is a substantially Y-shaped memberhaving a pair of ends at one end thereof attached to said central memberand circumscribing a portion of said member, and the remaining endattached to said sheet such that when the key station is actuated, saidremaining end will initially bend and the central member will then pivotwithin said Y-shaped member at the junction of said ends of said memberto said central member to insure that the contact finger immediatelyadjacent said remaining end is last-to-make.

5. The apparatus as defined in claim 4 wherein said central member andcontact fingers thereon, said Y- shaped member, and said sheet areintegrally formed and are substantially coplanar when the key station isnot actuated.

6. The apparatus as defined in claim 1 wherein said coupling meanscomprises an arcuate segment of flexible conducting material positionedwithin said opening and having opposite ends coupled to said sheet atthe edge of said opening, and a pair of spaced arms of flexibleconductive material extending from said arcuate segment to said centralmember such that said arcuate segment circumscribes at least a portionof said central member and wherein said predetermined contact ispositioned on said central member between said spaced arms.

7. The apparatus as defined in claim 1 wherein said coupling meanscomprises first and second arms of flexible conductive material eachhaving one end joined to said central member in spaced relationship tothe other arm and remote ends joined to the edge of said sheet withinsaid opening and in spaced relationship such that when the key stationis actuated, said arms will initially bend about said remote end andsubsequently said central member will pivot at the junction of said oneend of said arms to said central member such that a contact fingerbetween said arms is last-tomake.

8. The apparatus as defined in claim 7 wherein said ends of said firstand second arms are narrower than the middle of said arms therebypermitting the bending and twisting of said arm ends to provide thedesired motion for said movable contacts.

9. The apparatus as defined in claim 8 in which said first and secondarms are aligned in parallel relationship.

10. In a keyboard for developing electrical data signals uniquelyidentifying each of a plurality of key stations on said keyboard, anelectrical switch for each key station including a movable contact forcontacting an array of associated fixed electrical contacts coupled to asource of electrical power to provide an electrical data signal at anoutput terminal of said keyboard when a key station is actuated, saidmovable contact comprising:

a central member including a plurality of integrally formed contactfingers around the periphery of said central member, said central memberformed in a sheet of flexible conducting material mounted in proximityto the array of fixed contacts associated with a key station andcircumscribed by said sheet, said central member joined to said sheet bya joining member of flexible conducting material joining said centralmember to said sheet in a cantilevered fashion such that said centralmember and contact fingers thereon can be displaced relative to theplane of said sheet in a controlled manner to assure said contactfingers of said movable contact physically and electrically contact saidassociated array of fixed contacts whereby preselected contact fingersare last in the sequence of engagement to contact associated fixedcontacts when the key station is actuated.

11. The movable contact as defined in claim 10 wherein said joiningmember comprises an arcuate member having one edge coupled to said sheetand a pair of ends coupled to said central member such that said centralmember is partially circumscribed by said arcuate member.

12. The movable contact as defined in claim 11 wherein said centralmember, said joining member, and said sheet are integrally formed in asingle sheet of conducting material and in substantially the same plane.

13. The movable contact as defined in claim 10 wherein said joiningmember comprises a pair of arms coupled to said central member at spacedpositions on either side of said central member by one end of each arm,said arms having ends remote from the central member joined in spacedrelationship to said sheet.

14. The movable contact as defined in claim 13 wherein said centralmember and contact fingers thereon, said pair of arms, and said sheetare integrally formed in a single sheet of conducting material and insubstantially the same plane.

15. The movable contact as defined in claim 14 wherein each end of eachof said arms is narrowed to increase the flexibility of the arms at thejunction of said arms to said central member and to said sheet.

16. In an electrical-mechanical keyboard for providing electrical dataoutput signals which uniquely identify each key station of the keyboard,and wherein each key station comprises an array of fixed electricalswitch contacts and a single movable electrical contact which is movableto electrically contact the array of fixed electrical contacts; a methodof providing a signal indicating that each of the fixed contacts of thearray of fixed contacts have been contacted by the movable contactcomprising the steps of:

suspending the movable electrical contact in a cantilevered fashionabove the array of associated fixed electrical contacts;

bending the movable contact toward the array of fixed contacts at anangle thereto until at least one fixed contact is contacted by themovable contact; pivoting the movable contact such that it is parallelto the plane of the fixed contacts such that one of the remaining fixedcontacts contacts an associated contact in the sequence of engagement;and coupling the last-to-make electrical switch contact to an electricalcircuit which responds thereto to provide a signal when the last-to-makecontact is closed.

1. In a keyboard including a plurality of key stations for providingelectrical data signals uniquely identifying each key station as it isactuated, an electrical switch for each key station comprising: aninsulated base member; an array of fixed electrical contacts positionedin fixed relationship on said base member; insulative spacing means onsaid base member adjacent said array of fixed electrical contacts; asheet of flexible conducting material supported on said spacing means inspaced relationship to said array of fixed electrical contacts andincluding an opening therein; a movable electrical contact positionedwithin said opening of said sheet, said movable contact including acentral member with a plurality of contact fingers positioned inalignment with associated fixed electrical contacts and means couplingsaid central member to an edge of said sheet adjacent said opening in amanner such that when the key station is actuated, said central membermoves in a controlled manner to assure a predetermined contact fingerwill contact an associated fixed contact last in the sequence ofengagement of said contact fingers to said fixed contacts.
 2. Theapparatus as defined in claim 1 wherein said coupling means comprises anarcuate segment of flexible conducting material having opposite endscoupled to said central member such that said segment circumscribes aportion of said central member, and means for joining an edge of saidsegment remote from said central member to an edge of said sheet withinsaid opening in a cantilevered fashion such that when the key station isactuated, said central member will initially bend about said joiningmeans and subsequently pivot within said segment at the junction of saidopposite ends of said segment to said central member such that thecontact finger immediately adjacent said joining means is last-to-make.3. The apparatus as defined in claim 2 wherein said joining meanscomprises an arm coupled between said segment and said edge of saidsheet; and wherein said central member and contact fingers thereon, saidsegment, and said arm are integrally formed in said sheet and aresubstantially coplanar therewith when the key station is not actuated.4. The apparatus as defined in claim 1 wherein said means for couplingsaid central member to said sheet is a substantially Y-shaped memberhaving a pair of ends at one end thereof attached to said central memberand circumscribing a portion of said member, and the remaining endattached to said sheet such that when the key station is actuated, saidremaining end will initially bend and the central member will then pivotwithin said Y-shaped member at the junction of said ends of said memberto said central member to insure that the contact finger immediatelyadjacent said remaining end is last-to-make.
 5. The apparatus as definedin claim 4 wherein said central member and contact fingers thereon, saidY-shaped member, and said sheet are integrally formed and aresubstantially coplanar when the key station is not actuated.
 6. Theapparatus as defined in claim 1 wherein said coupling means comprises anarcuate segment of flexible conducting material positioned within saidopening and having opposite ends coupled to said sheet at the Edge ofsaid opening, and a pair of spaced arms of flexible conductive materialextending from said arcuate segment to said central member such thatsaid arcuate segment circumscribes at least a portion of said centralmember and wherein said predetermined contact is positioned on saidcentral member between said spaced arms.
 7. The apparatus as defined inclaim 1 wherein said coupling means comprises first and second arms offlexible conductive material each having one end joined to said centralmember in spaced relationship to the other arm and remote ends joined tothe edge of said sheet within said opening and in spaced relationshipsuch that when the key station is actuated, said arms will initiallybend about said remote end and subsequently said central member willpivot at the junction of said one end of said arms to said centralmember such that a contact finger between said arms is last-to-make. 8.The apparatus as defined in claim 7 wherein said ends of said first andsecond arms are narrower than the middle of said arms thereby permittingthe bending and twisting of said arm ends to provide the desired motionfor said movable contacts.
 9. The apparatus as defined in claim 8 inwhich said first and second arms are aligned in parallel relationship.10. In a keyboard for developing electrical data signals uniquelyidentifying each of a plurality of key stations on said keyboard, anelectrical switch for each key station including a movable contact forcontacting an array of associated fixed electrical contacts coupled to asource of electrical power to provide an electrical data signal at anoutput terminal of said keyboard when a key station is actuated, saidmovable contact comprising: a central member including a plurality ofintegrally formed contact fingers around the periphery of said centralmember, said central member formed in a sheet of flexible conductingmaterial mounted in proximity to the array of fixed contacts associatedwith a key station and circumscribed by said sheet, said central memberjoined to said sheet by a joining member of flexible conducting materialjoining said central member to said sheet in a cantilevered fashion suchthat said central member and contact fingers thereon can be displacedrelative to the plane of said sheet in a controlled manner to assuresaid contact fingers of said movable contact physically and electricallycontact said associated array of fixed contacts whereby preselectedcontact fingers are last in the sequence of engagement to contactassociated fixed contacts when the key station is actuated.
 11. Themovable contact as defined in claim 10 wherein said joining membercomprises an arcuate member having one edge coupled to said sheet and apair of ends coupled to said central member such that said centralmember is partially circumscribed by said arcuate member.
 12. Themovable contact as defined in claim 11 wherein said central member, saidjoining member, and said sheet are integrally formed in a single sheetof conducting material and in substantially the same plane.
 13. Themovable contact as defined in claim 10 wherein said joining membercomprises a pair of arms coupled to said central member at spacedpositions on either side of said central member by one end of each arm,said arms having ends remote from the central member joined in spacedrelationship to said sheet.
 14. The movable contact as defined in claim13 wherein said central member and contact fingers thereon, said pair ofarms, and said sheet are integrally formed in a single sheet ofconducting material and in substantially the same plane.
 15. The movablecontact as defined in claim 14 wherein each end of each of said arms isnarrowed to increase the flexibility of the arms at the junction of saidarms to said central member and to said sheet.
 16. In anelectrical-mechanical keyboard for providing electrical data outputsignals which uniquely identify each key station of the keyboard, andwherein each key statIon comprises an array of fixed electrical switchcontacts and a single movable electrical contact which is movable toelectrically contact the array of fixed electrical contacts; a method ofproviding a signal indicating that each of the fixed contacts of thearray of fixed contacts have been contacted by the movable contactcomprising the steps of: suspending the movable electrical contact in acantilevered fashion above the array of associated fixed electricalcontacts; bending the movable contact toward the array of fixed contactsat an angle thereto until at least one fixed contact is contacted by themovable contact; pivoting the movable contact such that it is parallelto the plane of the fixed contacts such that one of the remaining fixedcontacts contacts an associated contact in the sequence of engagement;and coupling the last-to-make electrical switch contact to an electricalcircuit which responds thereto to provide a signal when the last-to-makecontact is closed.